With the institution, late in 1956, of more stringent methods of safety testing poliomyelitis vaccine, an investigation of the antigenic potency of poliomyelitis vaccine presently available on the commercial market seemed desirable. The present paper presents observations on the antigenic potency of such vaccine, as measured by serologic tests on serums of vaccinated children, and on the safety of vaccine used for this study.
Since this investigation was begun, few reports on the potency of commercially available vaccine have been published. Kelly and Dalldorf1 observed differences in potency as great as six-hundred-fold between various vaccine lots when antibody response in guinea pigs was used as a criterion of potency. Shaughnessy2 reported significant differences in antibody response after two injections of various commercial vaccines but found a satisfactory response with all vaccine lots after three injections. Gelfand et al.3 reported satisfactory results after two injections in children who